The invention relates to a dental matrix of the type of a flexible sheet strip made preferably from a transparent material such as Mylar (.TM.).
Matrixes of this type have been used for many decades as a tool for retaining a packed filling material in a tooth.
Various types of matrixes and different clamping devices for them have been suggested and described in prior art. Reference may be had, for instance to U.S. Pat. Nos. 4,909,736 (Ritter); 4,563,152 (McClure); 4,704,087 (Dragan); 4,824,365 (von Weissenfluh); 3,082,531 (Jacobson); 4,117,596 (Wallshein); 3,421,222 (Newman); 2,646,622 (Christie et al.); 2,196,896 (Dvorak) and many other references.
Despite a large number of various types of the matrixes and their clamping mechanisms, today's practitioners prefer, by and large, a flexible strip of Mylar.TM. which is preferred for the inherent strength of the material and relatively low manufacturing costs. A typical matrix strip is a rectangular band about 1/2 inch wide, approximately 4 inches long and about 0.001" thick. Most practitioners prefer to apply the strip and to manually hold it in place until the respective filling settles.
One of the problems with all types of the known strips is that they are difficult to conform exactly to the shape of the tooth as in most cases the width of the matrix is selected to extend over the entire height of an average human tooth. This arrangement often results in escape of some of the packed filling material above or below the applied matrix, hardening at points from which it has to be subsequently removed, for instance near the gums or on the incisive part of a tooth. There are known matrixes of this type where the width of the band is smaller than the height of the tooth. The drawback of this band is in that often it is of insufficient width to cover the entire surface of the filling packed in a cavity.
Thus, the practitioner usually maintains a supply of matrix bands of different widths to match the particular size requirement.
The flexible strip-like matrix is typically applied around at least about 75% of the periphery of the respective tooth. This results in that the strip has to be positioned between proximal tooth surfaces. It is not uncommon that interproximal surfaces of two adjacent teeth abut firmly against each other leaving only a small gap at the gingival interproximate portion at which the proximal surfaces are spaced apart. This often gives rise to difficulties in inserting the matrix as the strip has to be forced interproximate the teeth from their incisal edge toward the gingival part of the interproximate portion.